My car has just done 60k - the rears were recently done for the first time (discs and pads - cost a lot from BMW dealer). The front pads are original and have plenty left. It does mostly motorway miles but plenty of quick A and B road work too. I do very little town driving, and I switch the DSC to "DTC" or "fully off" for any really keen stuff. I guess some people's rear brake wear is to do with the DSC kicking in all the time.
I am always surprised at my low rates of brake wear on all my cars, I used to race and when I am going for it, I'm not shy of using the brakes very hard. Because I have a high-speed vibration on the fronts (that has been there since I bought the car) I have been through a few cycles of really getting heat into them, as when bedding in track pads, and it didn't seem to do much to the wear. Wheras, frequent DSC intervention seems to wear them really fast, from various posts on here. Odd - You'd think long heavy stops would wear them more.